1. Field of the Invention
The present disclosure relates to a novel Streptomyces scopuliridis strain having a weed-killing activity and a medium composition for mass production of the strain.
2. Description of the Related Art
Since there are numerous types of weeds, various classification methods exist. General classification methods used in agriculture include classification methods depending on life cycle and shapes of weeds. According to the classification method depending on a shape, weeds are classified into grass weeds, broadleaf weeds, cyperaceae weeds, and so forth depending on the shapes of weeds. According to classification method depending on the life cycle, weeds are classified into annual weeds, biennial weeds, perennial weeds, and so forth depending on how long the weeds live.
Grass weeds have well-distinguishable internodes in a stem, and alternate leaves stretching from nodes, wherein the leaves are divided into leaf sheaths to surround the stem for protection and a leaf blade in which leaf veins in narrow long shapes are formed in parallel. Grass weeds include Echinochloa utilis, Digotaris sanguinalis, Alopecurus aequalis, Setaria viridis, Phragmites communis, Miscanthus sinensis, and so forth. A broad leaf weed is a plant which does not belong to grass weeds or sedge weeds and literally refers to weeds having relatively broad leaves. A leaf, which is mostly in an oval shape, an eggshape, or a needle shape, has veins interlaced like a net. Numerous weeds frequently appearing around us are included in this category such as Conyza Canadensis, Trifolium repens, Artemisia princes, Cardamine komarovi, Amaranthus mangostanus, Monochoria vaginalis var. plantaginea, Potamogeton franchetii, and Bidens tripartite. Although weeds belonging to sedges share similar features with grass weeds, sedge weeds are distinguished by the fact that cross section of a stem is mostly in a triangle shape and there is no ligule or auricle. A leaf is narrow and has a ridge, and a pointed end. Also, a small flower is hung at a spikelet. Examples include Cyperus microiria, Cyperus serotinas, Eleocharis kuroguwai ohwi, Scirpus fluviatilis, Scirpus juncoides Roxb, and so forth.
Sciyos angulatus L., which is a naturalized annual plant of family Cucurbitaceae originated from North America, is a weed collectively appears, in domestically, residential areas, as well as, riverside, roadside, railroads, and farmland to thereby seriously destroy the ecosystem. Thus, Sciyos angulatus L. is designated as Invasive Alien Plant under Protection of Wild Fauna and Flora Act by Ministry of Environment. Since Sciyos angulatus L. vigorously grows, produces a large amount of seeds, and forms a colony to grow, Sciyos angulatus L. causes herbaceous plants and trees to be withered by covering the plants and trees and inhibiting photosynthesis; changes in biodiversity by depriving and disturbing water and nitrogen in soil to thereby destroy existing vegetation; and also causes direct damage to human and livestock by inducing dermatitis due to a prickle on a surface of the seed. Currently, Sciyos angulatus L. is distributed to whole areas of Korea, and the distribution area thereof has been spearing, thereby leading to serious damage. Thus it is urgently required to develop a control technique for Sciyos angulatus L. control.
A method for removing Sciyos angulatus L. known so far is to cut or pull out plantlet which needs intensive labor. Sciyos angulatus L. which appears in some farms, may be partially controlled by using a non-selective organic synthetic herbicide such as glyphosate, however, control using an organic synthetic herbicide is extremely limited in practical because major birthplace and habitat of Sciyos angulatus L. are riverside, roadside, or residential areas where people live.
Moreover, problems caused by continuous use of an organic synthetic herbicide have been raised such as appearances of resistant weeds, potential influence on the ecosystem, and environmental pollution. In addition, as interest in environmentally friendly agriculture is increased due to an increase in income and the trend of emphasizing quality of life, in various countries of the world, regulation for reducing a use of a synthetic agricultural pesticide is strengthened. Therefore, it becomes more difficult to control Sciyos angulatus L. mainly appearing residential areas by using the conventional organic synthetic herbicide.
Thus, it is urgently required a technique for environmental friendly control of Sciyos angulates L. by using a natural substance or a biochemical preparation which can be easily degraded under the natural condition and has low toxicity to human and livestock.
Although an organic synthetic herbicide has been used for a long time due to the low cost and the high weed-killing activity, an interest has been increased to develop an environmentally friendly herbicide which is biodegradable and has low toxicity and selectivity because of appearance of resistant weeds and environmental pollution caused by continuous use. In particular, a material having a weed-killing activity produced by a microorganism including actinomyces has high efficiency and an environmentally friendly property, and thus the material has been noted as an experimental material and also for industrial application.
Actinomyces including Streptomyces sp., which is a gram-positive soil microorganism growing in a spawn form, produces various types of beneficial secondary metabolites in addition to an antibiotic material such as a herbicide. Thus, actinomyces has been received attention by researchers in term of study or an industrial application. Examples of a material having a weed killing activity, to which a secondary metabolite produced by actinomyces is applied, include herbicidin and herbimycin produced by Streptomyces saganonensis, anismycin produced by S. actinomycetes, bialaphos produced by S. viridochromogenes, albucidin produced by S. albus subsp. chlorinus NRRL B-24108, and glufosinate-ammonium isolated from S. viridichromogenes and S. hygroscopicus. Among them, bialophos and ansamitocins are commercialized and sold.
Despite of many cases of study, it is extremely limited to develop a natural and safe herbicide for weed control having an excellent weed-killing activity and low toxicity. Also, most of microorganism herbicides or herbicides derived from a plant under study and development are targeted to weeds appearing in farmland. Thus, it is still required to discover a novel microorganism which can be used as an environmentally friendly natural pesticide having the excellent weed-killing activity and low toxicity. Also, there is an emerging need to select an optimized medium which can expand growth of a microorganism and improve production of an active material while economically reducing a cost to increase a value of the Streptomyces sp. strain in an application as a material for natural herbicide.
For culture of a microorganism, saccharides including glucose, sugar, and maltose, etc., a glucose extract, and various types of starch are used as a carbon source; and an organic nitrogen source such as a beef extract, a malt extract, an yeast extract, soybean meal, and peptone and an inorganic nitrogen source such as ammonia water, ammonia sulfate ((NH4)2SO4), urea, and nitrate salts are used as a nitrogen source. In addition, a trace element such as a mineral and a vitamin is used to help bacterial growth and production of a secondary metabolite. These are most essential elements for culture of a microorganism which cause differences to be made in bacterial growth, and production and types of the secondary metabolite depending on combination and a composition ratio thereof.
Therefore, during an attempt to find an environmentally friendly natural product-derived herbicide and a method for mass producing the same, the present inventors have completed the present invention by verifying that: a novel Streptomyces scopuliridis KR-001 strain, a culture broth thereof, or a fraction of the culture shows the weed-killing ability on grass weeds, broad leaf weeds, and hard to control weeds; and that an optimal condition to reduce the unit cost of production is established by selecting a carbon source and a nitrogen source which increase yield of the active material produced by the strain so that it has been found that the strain can be usefully applied for mass production of a natural substance-derived weed control material.